System and method for manufacturing optical display device, set of material rolls and method for manufacture thereof

ABSTRACT

There are provided a system and a method for manufacturing an optical display device, in which optical films fed from two rolls which are the same in the direction of optical anisotropy, such as the direction of absorption axis, can be bonded to one and the other surfaces of an optical display unit so that the optical anisotropy of the one can be orthogonal to that of the other, and a set of material rolls and a method for manufacture thereof. A first optical film F 11  with a width corresponding to the short side of an optical display unit W has score lines that are previously formed so that the first optical film F 11  can be divided by the score lines into pieces each having a length corresponding to the long side of the optical display unit W. A second optical film F 21  with a width corresponding to the long side of the optical display unit W has score lines that are previously formed so that the second optical film F 21  can be divided by the score lines into pieces each having a length corresponding to the short side of the optical display unit W. A first bonding apparatus  18  bonds a divided piece of the first optical film F 11  with a length corresponding to the long side of the optical display unit W to one surface of the optical display unit W. A second bonding apparatus  28  bonds a divided piece of the second optical film F 21  with a length corresponding to the short side of the optical display unit W to the other surface of the optical display unit W.

TECHNICAL FIELD

The invention relates to a system and a method for manufacturing anoptical display device, which is for use in bondingoptically-anisotropic optical films, such as polarizing plate-containingoptical films, to one and the other surfaces of a rectangular opticaldisplay unit, and to a set of material rolls and a method for themanufacture thereof.

BACKGROUND ART

FIG. 8 schematically shows a conventional method for manufacturing anoptical display unit to be incorporated into a liquid crystal displaydevice. First, an optical film manufacturer produces a belt-shaped sheetmaterial, which includes an optical film, in the form of a roll (#1).Specific processes for the manufacture thereof are known, and thereforea description thereof is omitted. The roll of the belt-shaped sheetmaterial typically includes a raw polarizing plate, a raw retardationplate, or a raw laminated film of a polarizing plate and a retardationplate for use in the production of liquid crystal displays. The longmaterial is then stamped into pieces of the sheet material having ashape according to the size of an optical display unit to which eachpiece will be bonded (#2). Each piece of the sheet material (opticalfilm) obtained by the stamping is then subjected to an appearanceinspection (#3). Examples of the inspection method include a visualinspection for defects and an inspection using a known defect inspectionapparatus. The term “defect” typically means fouling of the surface orthe inside, scratches, a foreign substance-containing defect with aspecial shape such as a dented and twisted shape (also called “knick”),bubbles, foreign substances, etc. The finished product is then inspected(#4). The finished product inspection is performed according to morestrict quality criteria than those for the appearance inspection todetermine whether the product is non-defective. Subsequently, the fourend faces of each piece of the sheet material are worked (#5). Theworking is performed to prevent the pressure-sensitive adhesive or anyother material from coming out of the end faces in transit. Each pieceof the sheet material is then subjected to clean packaging in a cleanroom environment (#6). Subsequently, packaging for transportation(transport packaging) is performed (#7). Each piece of the sheetmaterial manufactured as described above is transported to a panelprocessing manufacturer.

The panel processing manufacturer unpacks the piece of the materialsheet transported (#11). An appearance inspection is then performed tocheck whether scratches, stains or other defects are produced in transitor during unpacking (#12). The piece of the sheet material determined tobe non-defective by the inspection is then transferred to the next step.This appearance inspection may be omitted in some cases. The opticaldisplay unit (such as a glass substrate unit with a sealed liquidcrystal cell) to which the piece of the sheet material will be bonded ispreviously manufactured and cleaned before the bonding step (#13).

The piece of the sheet material and the optical display unit are bondedtogether (#14). The release film is peeled off from the piece of thesheet material so that the pressure-sensitive adhesive can be left, andthe bonding surface of the pressure-sensitive adhesive layer is attachedto one side of the optical display unit. The other side of the opticaldisplay unit may also be subjected to a similar bonding process. Theoptical films to be bonded to both sides of the optical display unit mayhave the same structure or different structures. The optical displaydevice having the bonded optical film is then subjected to an inspectionand a defect inspection (#15). The optical display device determined tobe non-defective by the inspection is transferred to an implementingprocess (#16). On the other hand, the optical display device determinedto be defective is subjected to a reworking process (#17). In thereworking process, the optical film is peeled off from the opticaldisplay unit. A new optical film is bonded to the optical display unithaving undergone the reworking process (#14).

The manufacturing process described above particularly requires thesteps of working the end faces, packaging each piece of the sheetmaterial, and unpacking the material, because the optical filmmanufacturer and the panel processing manufacturer are located atdifferent places. However, such a multi-step process has the problem ofan increase in manufacturing cost. There are also problems in whichscratches, dust, stains, and the like can be caused by the multi-stepprocess or the transportation so that an inspection process can benecessary, and problems in which different types of sheet materials mustbe carried and managed.

Japanese Patent Application Laid-Open (JP-A) No. 2007-140046 (PatentDocument 1) discloses a method to solve the problems. A system by themethod includes means for drawing and feeding a belt-shaped sheetmaterial from a roll of the belt-shaped sheet material including anoptical film to be used as a component of an optical display device,means for detecting defects in the belt-shaped sheet material drawn fromthe feeding means, means for cutting the belt-shaped sheet material intosheet material pieces based on the result of the detection by thedetecting means, means for transporting each sheet material piece cut bythe cutting means to a bonding process, and means for bonding thetransported sheet material piece to an optical display unit as acomponent of the optical display device, wherein the respective meansare arranged on a continuous production line. In this system, thebelt-shaped sheet material including the optical film can be directlycut into the desired size, and the cut piece of the sheet material canbe directly bonded to the optical display unit. According to aconventional technique, the belt-shaped sheet material is stamped intopieces, and the stamped sheet material pieces are each carefullypackaged and delivered to a panel processing manufacturer. According tothis system, however, a roll of the belt-shaped sheet material can bedirectly packaged and delivered.

PRIOR ART LITERATURE Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No.    2007-140046

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, the optical display device manufacturing system disclosed inPatent Document 1 does not include any additional apparatus for bondinganother optical film to the other side of the optical display unit afterthe bonding of an optical film to one side of the optical display unit.Therefore, if the same manufacturing system is used to bond anotheroptical film to the other side, loading the optical display unit on thesystem after the bonding results in double work, and there is a room forimprovement.

When bonded to one and the other surfaces of an optical display unit,polarizing plates have different absorption axis directions (crossingeach other at right angles) on the one and the other surfaces. Inaddition, it is generally difficult to produce a material roll having anabsorption axis in the width direction of the roll, whereas the opticaldisplay unit generally has a rectangular shape. Considering thesethings, a satisfactory system configuration cannot be obtained by simplyadding each of means for performing the process from the feeding of thebelt-shaped sheet material to the bonding thereof to the manufacturingsystem disclosed in Patent Document 1.

Not only when polarizing plates are placed on one and the othersurfaces, but also, for example, when retardation plates are placed onone and the other surfaces of the optical display unit, their slow axisdirections on the one and the other surfaces have to be perpendicular toeach other in some cases. Also in such cases, there is the same problemas in the case where polarizing plates are laminated.

It is therefore an object of the invention to provide a system and amethod for manufacturing an optical display device, in which opticalfilms can be bonded to one and the other surfaces of an optical displayunit in such a manner that the optical anisotropy of the one isorthogonal to that of the other by using two material rolls that are thesame in the direction of optical anisotropy, such as the direction ofabsorption axis, and to provide a set of material rolls and a method formanufacture thereof.

Means for Solving the Problem

The above object can be achieved by the present inventions as follows.That is, a system for manufacturing an optical display device of thepresent invention is a system for manufacturing an optical displaydevice comprising a rectangular optical display unit and anoptically-anisotropic optical film bonded to the optical display unit,and comprises:

-   -   a first bonding apparatus for bonding a divided piece of a first        optical film to one surface of an optical display unit, wherein        the divided piece of the first optical film has a length        corresponding to a long side of the optical display unit and is        obtained from a roll of a belt-shaped sheet material that        comprises the first optical film and has score lines that are        previously formed so that the first optical film can be divided        by the score lines into pieces each having a length        corresponding to the long side of the optical display unit,        wherein the first optical film has a width corresponding to a        short side of the optical display unit; and    -   a second bonding apparatus for bonding a divided piece of a        second optical film to another surface of the optical display        unit, wherein the divided piece of the second optical film has a        length corresponding to the short side of the optical display        unit and is obtained from a roll of a belt-shaped sheet material        that comprises the second optical film and has score lines that        are previously formed so that the second optical film can be        divided by the score lines into pieces each having a length        corresponding to the short side of the optical display unit,        wherein the second optical film has a width corresponding to the        long side of the optical display unit.

In the optical display device manufacturing system of the invention,divided pieces of optical films with sizes corresponding to the shortand long sides of the optical display unit can be obtained,respectively, only by dividing, by each score line, the optical film fedfrom each of a material roll with a width corresponding to the shortside of the optical display unit and a material roll with a widthcorresponding to the long side of the optical display unit. The formerand the latter are each divided by each score line into a piece with alength corresponding to the long side and a piece with a lengthcorresponding to the short side, and the pieces are bonded to bothsurfaces of the optical display unit. Therefore, when two material rollsthat are the same in the direction of optical anisotropy, such as thedirection of absorption axis are used, optical films can be bonded toone and the other surfaces of the optical display unit in such a mannerthat the optical anisotropy of one of the optical films is orthogonal tothat of the other optical film.

Also, a system for manufacturing an optical display device of thepresent invention is a system for manufacturing an optical displaydevice comprising a rectangular optical display unit and an optical filmincluding a polarizing plate and bonded to the optical display unit, andcomprises:

-   -   an optical display unit feeding apparatus for feeding the        optical display unit;    -   a first optical film feeding apparatus for drawing and feeding a        belt-shaped sheet material from a roll of the belt-shaped sheet        material, wherein the belt-shaped sheet material comprises a        first optical film with a width corresponding to a short side of        the optical display unit and has score lines that are previously        formed so that the first optical film can be divided by the        score lines into pieces each having a length corresponding to a        long side of the optical display unit;    -   a first bonding apparatus for bonding a divided piece of the        first optical film to one surface of the optical display unit,        wherein the optical display unit is fed from the optical display        unit feeding apparatus, and the first optical film is fed from        the first optical film feeding apparatus;    -   a feeder for transporting and feeding the optical display unit        after the bonding of the first optical film;    -   a second optical film feeding apparatus for drawing and feeding        a belt-shaped sheet material from a roll of the belt-shaped        sheet material, wherein the belt-shaped sheet material comprises        a second optical film with a width corresponding to the long        side of the optical display unit and has score lines that are        previously formed so that the second optical film can be divided        by the score lines into pieces each having a length        corresponding to the short side of the optical display unit; and    -   a second bonding apparatus for bonding a divided piece of the        second optical film to another surface of the optical display        unit, wherein the optical display unit is fed from the feeder,        and the second optical film is fed from the second optical film        feeding apparatus.

The optical display device manufacturing system of the invention furtherincludes the feeder, the second optical film feeding apparatus, and thesecond bonding apparatus as stated above and is also configured so thatthe first and second optical film feeding apparatuses can feed dividedpieces of optical films with different widths and lengths correspondingto the long and short sides of the optical display unit, respectively.Thus, using material rolls including polarizing plates with the sameabsorption axis direction, optical films can be bonded to one and theother surfaces of the optical display unit in a continuous manufacturingline.

In the above system, it is preferred that the feeder has a turningmechanism for turning the optical display unit to a bonding directionfor the second bonding apparatus after the bonding in the first bondingapparatus. The presence of such a turning mechanism makes it unnecessaryto vertically arrange a set of the first optical film feeding apparatusand the first bonding apparatus and a set of the second optical filmfeeding apparatus and the second bonding apparatus, which makes itpossible to save the space of the manufacturing system. The turningmechanism also makes it possible to set a proper bonding angle for thesecond bonding apparatus. Specifically, higher turning position accuracycan be obtained when the optical display unit, which is harder than theoptical film, is turned than when the flexible material such as theoptical film is turned.

Also, it is preferred that the first and second optical film feedingapparatuses each has a defective portion removing mechanism for removinga defective divided piece of the optical film. The presence of such aremoving mechanism makes it possible to remove defective portions fromthe optical film and to improve the optical film yield.

Further, it is preferred that the first and second optical film feedingapparatuses have feeding mechanisms for feeding the first and secondoptical films to the first and second bonding apparatuses, respectively,by using, as a carrying medium, a release film which is provided on theoptical film with a pressure-sensitive adhesive layer interposedtherebetween. When such a feeding mechanism is provided, the first andsecond optical films can be fed with high accuracy to the first andsecond bonding apparatuses, respectively, using a simple feedingmechanism.

On the other hand, a method for manufacturing an optical display deviceof the present invention is a method for manufacturing an opticaldisplay device comprising a rectangular optical display unit and anoptically-anisotropic optical film bonded to the optical display unit,and comprises:

-   -   a first bonding step comprising: providing a roll of a        belt-shaped sheet material that comprises a first optical film        with a width corresponding to a short side of the optical        display unit and has score lines that are previously formed so        that the first optical film can be divided by the score lines        into pieces each having a length corresponding to a long side of        the optical display unit; and bonding a divided piece of the        first optical film having a length corresponding to the long        side of the optical display unit to one surface of the optical        display unit; and    -   a second bonding step comprising: providing a roll of a        belt-shaped sheet material that comprises a second optical film        with a width corresponding to the long side of the optical        display unit and has score lines that are previously formed so        that the second optical film can be divided by the score lines        into pieces each having a length corresponding to the short side        of the optical display unit; and bonding a divided piece of the        second optical film having a length corresponding to the short        side of the optical display unit to another surface of the        optical display unit.

In the optical display device manufacturing method of the invention, amaterial roll with a width corresponding to the short side of theoptical display unit and a material roll with a width corresponding tothe long side of the optical display unit are used, and the former andthe latter are each divided by each score line into a piece with alength corresponding to the long side and a piece with a lengthcorresponding to the short side, and the pieces are bonded to bothsurfaces of the optical display unit. Therefore, when two material rollsthat are the same in the direction of optical anisotropy, such as thedirection of absorption axis are used, optical films can be bonded toone and the other surfaces of the optical display unit in such a mannerthat the optical anisotropy of one of the optical films is orthogonal tothat of the other optical film.

In the above method, it is preferred that the method further comprises aturning step comprising turning the optical display unit to a bondingdirection for the second bonding step after the first bonding step. Sucha turning step makes it unnecessary to vertically arrange the first andsecond optical film feed directions, which makes it possible to save thespace of the manufacturing system. The use of the turning step alsomakes it possible to set a proper bonding angle for the second bondingapparatus.

Also, it is preferred that the method further comprises a defectiveportion removing step comprising removing a defective divided piece ofthe optical film when the first and second optical films are each fed.Such a removing step makes it possible to remove defective portions fromthe optical film and to improve the optical film yield.

Further, it is preferred that the first and second optical films aretransported and fed to the first and second bonding steps, respectively,using, as a carrying medium, a release film which is provided on theoptical film with a pressure-sensitive adhesive layer interposedtherebetween. When such a feeding method is used, the first and secondoptical films can be fed with high accuracy to the first and secondbonding steps, respectively, using a simple feeding mechanism.

A set of material rolls of the invention comprises:

-   -   a first roll comprising a first optical film to be bonded to one        surface of a rectangular optical display unit,    -   the first roll comprising a first belt-shaped sheet material        that comprises the first optical film, a first        pressure-sensitive adhesive layer, and a first release film        laminated in this order, wherein the first optical film        comprises a first polarizing plate whose longitudinal direction        is parallel to its absorption axis, the first belt-shaped sheet        material having score lines that are previously formed so that        the first optical film can be divided by the score lines into        pieces each having a length corresponding to a long side of the        optical display unit,    -   the first belt-shaped sheet material having undergone a slitting        process in a direction parallel to the longitudinal direction of        the first polarizing plate so that it has a width corresponding        to a short side of the optical display unit, and having been        wound into the roll; and    -   a second roll comprising a second optical film to be bonded to        another surface of the optical display unit,

the second roll comprising a second belt-shaped sheet material thatcomprises the second optical film, a second pressure-sensitive adhesivelayer, and a second release film laminated in this order, wherein thesecond optical film comprises a second polarizing plate whoselongitudinal direction is parallel to its absorption axis,

-   -   the second belt-shaped sheet material having score lines that        are previously formed so that the second optical film can be        divided by the score lines into pieces each having a length        corresponding to a short side of the optical display unit,    -   the second belt-shaped sheet material having undergone a        slitting process in a direction parallel to the longitudinal        direction of the second polarizing plate so that it has a width        corresponding to the long side of the optical display unit, and        having been wound into the roll.

The set of material rolls according to the invention includes a firstroll having undergone slitting into a width corresponding to the shortside of the optical display unit; and a second roll having undergoneslitting into a width corresponding to the long side of the opticaldisplay unit. Therefore, when the set is used, divided pieces of opticalfilms with sizes corresponding to the short and long sides of theoptical display unit can each be obtained only by dividing, by eachscore line, the optical film fed from each of the rolls. In this case,since both roll materials have an absorption axis in the longitudinaldirection, the bonding can be performed with good axis accuracy, so thatthe optical display device can have good optical properties after thebonding. In addition, the respective optical films have absorption axes,one of which can be parallel to the long side of the optical displayunit, and the other of which can be parallel to the short side.Therefore, the absorption axes of the optical films can be madeperpendicular to each other only by bonding them to one and the othersurfaces of the optical display unit, respectively. Thus, there isprovided a set of material rolls with which optical films can be bondedwith their absorption axes perpendicular to each other to the opticaldisplay unit only through the process of dividing, by each score line,the optical film fed from each of the two material rolls, which canprovide high axis accuracy for the bonding.

It is preferred that the optical display unit to be subjected to thebonding is a VA or IPS mode liquid crystal panel. Particularly when theoptical display unit is formed using a VA or IPS mode liquid crystalpanel, which has been recently used in large screen TVs, etc., thepolarizing plates of the first and second optical films can bepositioned so that their absorption axes are perpendicular to each otherand parallel to the side of the rectangular liquid crystal panel. Inthis case, therefore, the optical film can be simply divided by eachscore line, while each of the first and second material rolls havingundergone slitting parallel to the absorption axis is unwound, so that ahigh production rate is possible.

A manufacturing method for a material roll of the invention is amanufacturing method for a material roll used in the set of materialrolls, and comprises the steps of:

-   -   slitting a material having undergone no slitting process to form        a belt-shaped sheet material with a width corresponding to the        long or short side of the optical display unit, wherein the        material comprises an optical film, a pressure-sensitive        adhesive layer, and a release film laminated in this order, the        optical film comprises a polarizing plate whose longitudinal        direction is parallel to its absorption axis, and the slitting        is performed parallel to the longitudinal direction of the        polarizing plate; and    -   winding the resulting belt-shaped sheet material into a roll.

According to the material roll manufacturing method of the invention,slitting into a width corresponding to the short or long side of theoptical display unit is performed, so that an optical film with a sizecorresponding to the short or long side of the optical display unit canbe obtained only by dividing the material by each score line. Inaddition, since the unslit material used has a longitudinal directionparallel to the absorption axis of the polarizing plate, the bonding canbe performed with good axis accuracy in the manufacturing process, sothat the optical display device can have good optical properties afterthe bonding.

A material roll of the invention comprises an optical film to be bondedto a surface of a rectangular optical display unit, comprising:

-   -   a belt-shaped sheet material that comprises the optical film, a        pressure-sensitive adhesive layer, and a release film laminated        in this order, wherein the optical film comprises a polarizing        plate whose longitudinal direction is parallel to its absorption        axis,    -   the belt-shaped sheet material having score lines that are        previously formed so that the optical film can be divided by the        score lines into pieces each having a length corresponding to a        long or short side of the optical display unit,    -   the belt-shaped sheet material having undergone a slitting        process in a direction parallel to the longitudinal direction of        the polarizing plate so that it has a width corresponding to the        short or long side of the optical display unit, and having been        wound into the roll.

The material roll of the invention is a roll of a material havingundergone slitting into a width corresponding to the short or long sideof the optical display unit. Therefore, an optical film with a sizecorresponding to the short or long side of the optical display unit canbe obtained only by dividing the material by each score line. Inaddition, since slitting has been performed in the longitudinaldirection parallel to the absorption axis of the polarizing plate, thebonding can be performed with good axis accuracy in the manufacturingprocess, so that the optical display device can have good opticalproperties after the bonding.

A method for manufacturing a material roll of the invention is a methodfor manufacturing a material roll comprising an optical film to bebonded to a surface of a rectangular optical display unit, and comprisesthe steps of:

-   -   slitting a material having undergone no slitting process to form        a belt-shaped sheet material with a width corresponding to a        short or long side of the optical display unit, wherein the        material comprises the optical film, a pressure-sensitive        adhesive layer, and a release film laminated in this order and        has score lines that are previously formed so that the optical        film can be divided by the score lines into pieces each having a        length corresponding to the long or short side of the optical        display unit, the optical film comprises a polarizing plate        whose longitudinal direction is parallel to its absorption axis,        and the slitting is performed parallel to the longitudinal        direction of the polarizing plate; and    -   winding the resulting belt-shaped sheet material into a roll.

According to the material roll manufacturing method of the invention,slitting into a width corresponding to the short or long side of theoptical display unit is performed, so that an optical film with a sizecorresponding to the short or long side of the optical display unit canbe obtained only by dividing the material by each score line. Inaddition, since the unslit material used has a longitudinal directionparallel to the absorption axis of the polarizing plate, the bonding canbe performed with good axis accuracy in the manufacturing process, sothat the optical display device can have good optical properties afterthe bonding.

A method for manufacturing an optical display device of the invention isa method for manufacturing an optical display device comprising anoptical film including a polarizing plate and a rectangular opticaldisplay unit having a surface to which the optical film is bonded, andcomprises the steps of:

-   -   providing a material roll that is a roll of a belt-shaped sheet        material obtained by slitting a material having undergone no        slitting process into a width corresponding to a short or long        side of the optical display unit, wherein the material comprises        the optical film, a pressure-sensitive adhesive layer, and a        release film laminated in this order and has score lines that        are previously formed so that the optical film can be divided by        the score lines into pieces each having a length corresponding        to the long or short side of the optical display unit, the        optical film comprises a polarizing plate whose longitudinal        direction is parallel to its absorption axis, and the slitting        is performed parallel to the longitudinal direction of the        material;    -   drawing the belt-shaped sheet material from the material roll;        and    -   bonding a divided piece of the optical film to a surface of the        rectangular optical display unit.

According to the optical display device manufacturing method of theinvention, the material roll used has undergone slitting into a widthcorresponding to the short or long side of the optical display unit, andtherefore, an optical film with a size corresponding to the short orlong side of the optical display unit can be obtained only by dividingthe material by each score line. In addition, since the unslit materialused has a longitudinal direction parallel to the absorption axis of thepolarizing plate, the bonding can be performed with good axis accuracyin the manufacturing process, so that the optical display device canhave good optical properties after the bonding.

A system for manufacturing an optical display device of the invention isa system for manufacturing an optical display device comprising anoptical film including a polarizing plate and a rectangular opticaldisplay unit having a surface to which the optical film is bonded, andcomprises:

-   -   a bonding apparatus for drawing a belt-shaped sheet material        from a roll of the belt-shaped sheet material and bonding a        divided piece of the optical film to the rectangular optical        display unit, wherein    -   the belt-shaped sheet material is obtained by slitting a        material having undergone no slitting process into a width        corresponding to a short or long side of the optical display        unit, wherein the material comprises the optical film, a        pressure-sensitive adhesive layer, and a release film laminated        in this order and has score lines that are previously formed so        that the optical film can be divided by the score lines into        pieces each having a length corresponding to the long or short        side of the optical display unit, the optical film comprises a        polarizing plate whose longitudinal direction is parallel to its        absorption axis, and    -   the slitting is performed parallel to the longitudinal direction        of the material.

According to the optical display device manufacturing system of theinvention, the material roll used has undergone slitting into a widthcorresponding to the short or long side of the optical display unit, andtherefore, an optical film with a size corresponding to the short orlong side of the optical display unit can be obtained only by dividingthe material by each score line. In addition, since the unslit materialused has a longitudinal direction parallel to the absorption axis of thepolarizing plate, the bonding can be performed with good axis accuracyin the manufacturing process, so that the optical display device canhave good optical properties after the bonding.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart showing a process performed using themanufacturing system of the invention;

FIG. 2 is a diagram for illustrating an example of the manufacturingsystem of the invention;

FIG. 3 is a diagram for illustrating an example of the manufacturingsystem of the invention;

FIG. 4 is a diagram for illustrating an example of the laminatedstructure of each of first and second optical films;

FIG. 5 is a perspective view of a first roll showing an example of thescore lines formed in a first sheet material;

FIG. 6 is a perspective view of a first roll showing another example ofthe score lines formed in a first sheet material;

FIG. 7 is a schematic diagram showing a specific example of the methodof turning the optical display unit over and by 90°; and

FIG. 8 is a flow chart of a conventional optical display devicemanufacturing method.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Embodiments of the invention are described below in the order ofmaterials used in the optical display device manufacturing system,manufacturing process flow, and the structure of each component of themanufacturing system. FIG. 1 shows an example of the flow chart of theoptical display device manufacturing method. FIG. 2 is a schematicdiagram showing an example of the optical display device manufacturingsystem. FIG. 3 is a layout plan view showing an example of the opticaldisplay device manufacturing system.

Optical Display Unit

The optical display unit for use in the invention is intended to includeany assembly of parts for displaying characters or images. The opticaldisplay unit is typically a liquid crystal cell, an organicelectroluminescence panel, or the like. The invention is effective whenusing an optical display unit having a rectangular outline shape, suchas that with a long side/short side ratio of 16/9 or 4/3. The opticaldisplay unit may also have such a member as an optical film that ispreviously integrated as part of the laminated structure.

Optical Film

The optical film to be bonded to the optical display unit may be amonolayer film or a multilayer film. The optical film has at least oneoptically anisotropic layer. The term “optically anisotropic” or“optical anisotropy” means that the in-plane optical properties are notuniform, and examples of optical anisotropy include absorptionanisotropy, refractive index anisotropy, and reflection anisotropy. Theoptical film is typically a polarizing plate having an absorption axis,a retardation film having a slow axis, a brightness enhancement filmhaving a transmission axis, or a laminate thereof.

The polarizing plate-containing optical film may be a polarizing plateor an optical film including a laminate of a polarizing plate and aretardation film, a brightness enhancement film, or a combination of twoor more of these films.

The belt-shaped sheet material for use in the invention is intended toinclude a long sheet that is processed to have a width corresponding tothe short or long side of the optical display unit and is sufficientlylonger in the longitudinal direction than in the width direction. Forexample, the length of the belt-shaped sheet material is 10 times ormore the width. The belt-shaped sheet material may be any materialcontaining the optical film. The belt-shaped sheet material preferablyincludes a polarizing plate-containing optical film, apressure-sensitive adhesive layer, and a release film, which areprovided in this order.

The material roll for use in the invention is a wound roll of thebelt-shaped sheet material. The material roll is usually obtained bywinding the belt-shaped sheet material around a roll core from one endthereof.

A protective transparent film is sometimes placed on the surface of anyof these optical films. For example, a pressure-sensitive adhesive layeris preferably formed on one surface of the optical film so that theoptical film can be bonded to the optical display unit, and a releasefilm should be provided to protect the pressure-sensitive adhesivelayer. A surface protecting film may be provided on the other surface ofthe optical film, for example, with a pressure-sensitive adhesive layerinterposed therebetween.

The invention is effective when using two material rolls having opticalanisotropy in the same direction, particularly using two material rollsin which the absorption axes of polarizing plates in optical films arein the same direction. The direction of the absorption axis of thepolarizing plate is generally in the longitudinal direction of thematerial roll. When a retardation film is used, the slow axis of theretardation film may be parallel or perpendicular to the longitudinaldirection of the material roll or oblique to the longitudinal directionof the material roll by a certain angle.

Manufacturing Flow Chart

The optical display device manufacturing method of the invention is amethod for manufacturing an optical display device including an opticaldisplay unit and an optically anisotropic optical film bonded to theoptical display unit, preferably a method for manufacturing an opticaldisplay device including an optical display unit and a polarizingplate-containing optical film bonded to the optical display unit.

The manufacturing method of the invention includes a first bonding stepand a second bonding step. The manufacturing method preferably furtherincludes a transporting and feeding step between the first and secondbonding steps. The first and second bonding steps may be performed inany order or at the same time.

The first bonding step includes: providing a roll of a belt-shaped sheetmaterial that includes a first optical film with a width correspondingto the short side of the optical display unit and has score lines thatare previously formed so that the first optical film can be divided bythe score lines into pieces each having a length corresponding to thelong side of the optical display unit; and bonding a divided piece ofthe first optical film having a length corresponding to the long side ofthe optical display unit to one surface of the optical display unit.

The second bonding step includes: providing a roll of a belt-shapedsheet material that includes a second optical film with a widthcorresponding to the long side of the optical display unit and has scorelines that are previously formed so that the second optical film can bedivided by the score lines into pieces each having a lengthcorresponding to the short side of the optical display unit; and bondinga divided piece of the second optical film having a length correspondingto the short side of the optical display unit to the other surface ofthe optical display unit.

More specifically, for example, the optical display device manufacturingmethod of the invention includes: a first bonding step including bondinga divided piece of the first optical film to one surface of the opticaldisplay unit, while drawing and feeding a belt-shaped sheet materialfrom a roll of the belt-shaped sheet material including the firstoptical film; and a second bonding step including bonding a dividedpiece of the second optical film to the other surface of the opticaldisplay unit, while drawing and feeding a belt-shaped sheet materialfrom a roll of the belt-shaped sheet material including the secondoptical film.

For example, the first bonding step may be performed by the process from(2) Feeding Step to (3) First Optical Film Bonding Step described below.For example, the second bonding step may be performed by the processfrom (6) Feeding Step to (7) Second Optical Film Bonding Step describedbelow.

(1) Step of Providing First Material Roll (S1 in FIG. 1). A first rollof a first belt-shaped sheet material is provided. The width of thefirst roll depends on the size of the optical display unit to be bonded.More specifically, the width of the first roll is determined tocorrespond to one of the long and short sides of the optical displayunit, and the width of the second roll is determined to correspond tothe other. Therefore, the first and second rolls have different widths,and material rolls having undergone no slitting process (unslitmaterials rolls) are each previously subjected to a slitting process soas to have a predetermined width, and the materials with thepredetermined widths are used.

The slitting process is performed while the material having undergone noslitting process (unslit material) is unwound from the roll. Theslitting process may be performed by a method using a laser cutter or anedge tool such as a rotary circular knife. The process of producing thematerial roll preferably includes slitting the unslit material in thelongitudinal direction and winding the resulting belt-shaped sheetmaterial into a roll. A conceivable method for producing a material rollwith a width corresponding to the long or short side of the opticaldisplay unit can include cutting the unslit material roll itself fromone or both ends thereof. In such a method, however, the unslit materialroll can be cut in such a condition that winding displacement occurs(such a condition that the roll does not have a flat end face), so thatthe axis direction of the optical film can be non-uniform in theproduced material roll. In contrast, when the slitting step is followedby the winding step as described above, the axis of the optical film inthe produced material roll has a uniform direction, so that the opticalfilm can be bonded to the optical display unit with high axis precision.The object to be slit does not have to be in the form of a roll such asa roll of an unslit material and may be an unwound long material (suchas a long material before wound up after produced). When the opticalfilm contains a polarizing plate, the absorption axis preferably extendsin the longitudinal direction of the long material. In such a case, thelong material is preferably slit parallel to the absorption axis, andthen the resulting belt-shaped sheet material is preferably wound into aroll.

As used herein, the expression “to correspond to the long or short sideof the optical display unit” means that the bonding length of theoptical film (exclusive of the length of the exposed portion) willcorrespond to the length of the long or short side of the opticaldisplay unit and does not mean that the width of the optical film has tobe equal to the length of the long or short side of the optical displayunit.

In an embodiment of the invention, each of the first and second rollscomprises a roll of a belt-shaped sheet material, which is obtained byslitting a polarizing plate (a component of the roll) parallel to theabsorption axis thereof, and has an absorption axis in the longitudinaldirection of the belt-shaped sheet material. This configuration provideshigh axis precision for the bonding, so that after the bonding, theoptical display device has good optical properties. Particularly whenthe optical display unit is formed using a VA or IPS mode liquid crystalpanel, which has been recently used in large screen TVs, etc., thepolarizing plates of the first and second optical films can bepositioned so that their absorption axes are perpendicular to eachother. In this case, therefore, divided pieces of the first and secondoptical films can be each simply bonded to the surface of the opticaldisplay unit, while the belt-shaped sheet material obtained by slittingthe long material parallel to its absorption axis is fed from each ofthe first and second rolls, so that a high production rate is possible.

For example, the influence of the axis precision during the bonding onthe optical properties may be evaluated using the transmitted lightintensity and contrast ratio (CR) described below. Specifically, abelt-shaped sheet material obtained by slitting a polarizing plate(CAT1463DU manufactured by NITTO DENKO CORPORATION)—containing longmaterial parallel to the absorption axis of the polarizing plate andanother belt-shaped sheet material obtained by slitting a polarizingplate-containing long material at a varied certain angle with respect tothe absorption axis of the polarizing plate were each cut into a squaresample piece (50 mm×50 mm) having a side parallel to the slittingdirection. The two sample pieces were laminated, and the transmittanceof the resulting laminate was measured using a spectrophotometer U-4100manufactured by Hitachi High-Technologies Corporation. The results areshown in Table 1.

TABLE 1 Transmitted light Axis angle intensity CR Comparative 6059.04759 1.693549 Example 1 Comparative 67.5 77.96201 1.282676 Example 2Comparative 82.5 19.6158 5.097931 Example 3 Example 1 90 0.04136072417.754 Comparative 97.5 20.27872 4.931278 Example 4 Comparative 112.578.09852 1.280434 Example 5 Comparative 120 56.95775 1.755687 Example 6

As is evident from the results in Table 1, a comparison between Example1 with the angle between the absorption axes is 90° and each comparativeexample where the angle between the absorption axes deviates from 90°shows that even a slight angular deviation from 90° causes significantlight leakage (transmitted light intensity) and a significant reductionin contrast ratio (CR).

As shown in FIG. 4, for example, the laminated structure of the firstsheet material F1 includes a first optical film F11, a first releasefilm F12, and a surface protecting film F13. The first optical film F11includes a first polarizer F11 a, a first film F11 b provided on oneside thereof with an adhesive layer (not shown) interposed therebetween,and a second film F11 c provided on the other side thereof with anadhesive layer (not shown) interposed therebetween.

For example, the first and second films F11 b and F11 c are polarizerprotecting films (such as triacetylcellulose films or PET films). Thesecond film F11 c is to be bonded to the surface of the optical displayunit with a first pressure-sensitive adhesive layer F14 interposedtherebetween. The first film F11 b may undergo a surface treatment.Examples of the surface treatment include a hard coating treatment, anantireflection treatment, and a treatment for any other purpose such asanti-sticking, diffusion or antiglare purpose. The first release filmF12 is provided on the second film F11 c with a first pressure-sensitiveadhesive layer F14 interposed therebetween. The surface protecting filmF13 is provided on the first film F11 b with a pressure-sensitiveadhesive layer F15 interposed therebetween. The specific structure ofthe first and second films F11 b and F11 c is described below.Hereinafter, a laminated structure of a polarizer and a polarizerprotecting film is also referred to as a polarizing plate.

In a factory, each step described below is performed in an isolatedstructure preferably with cleanliness maintained. In particular,cleanliness is preferably maintained in the step of bonding the opticalfilm to the optical display unit.

In an embodiment of the invention, the first sheet material F1 has scorelines that are previously formed so that the first optical film F11 canbe divided by the score lines into pieces each having a lengthcorresponding to the long side of the optical display unit. Each scoreline, which extends in the width direction of the first sheet materialF1, is typically formed by cutting the layers other than the firstrelease film F12 in the first sheet material F1. However, the layersother than the first release film F12 in the first sheet material F1 donot always have to be completely cut, and for example, at least onelayer such as the first pressure-sensitive adhesive layer F14 may alsobe not completely cut, or the score line may be in any other form suchas a perforation, as long as the first optical film F11 can be dividedby each score line.

FIG. 5 is a perspective view of the first roll showing an example of theformation of score lines in the first sheet material F1. In thisexample, score lines are formed in the first sheet material at regularintervals corresponding to the long side of the optical display unit.Therefore, the first optical film F11 is divided by each score line sothat a divided piece of the first optical film F11 with a sizecorresponding to that of the optical display unit can be obtained andbonded to the optical display unit.

FIG. 6 is a perspective view of the first roll showing another exampleof the formation of score lines in the first sheet material F1. In thisexample, the first sheet material F1 has a portion with score linesformed at an interval corresponding to the long side of the opticaldisplay unit and a portion with score lines formed at an intervaldifferent from the interval corresponding to the long side of theoptical display unit. When the first optical film F11 is divided by thescore lines, the portion with the score lines formed at an intervalcorresponding to the long side of the optical display unit forms adivided piece of the first optical film F11 with a size corresponding tothat of the optical display unit, which can be bonded to the opticaldisplay unit.

On the other hand, the portion with score lines formed at an intervaldifferent from the interval corresponding to the long side of theoptical display unit may be removed without being bonded to the opticaldisplay unit. For example, a method may be used which includesperforming inspection on the first sheet material F1 to detect anydefect in advance and forming score lines while avoiding the defect sothat the region to be bonded to the optical display unit does notinclude the defect (this method is called “skip cutting”). In this case,a divided piece containing the defect (the portion with score linesformed at an interval different from the interval corresponding to thelong side of the optical display unit) is removed by means of a firstrejection apparatus 19 as described below without being bonded to theoptical display unit, so that the optical film yield is improved. In anembodiment of the invention, therefore, the step of feeding the opticalfilm preferably includes a defective portion-removing step that includesremoving a defect-containing, divided piece of the optical film.

The defect inspection method may be a method of performing imaging andimage processing on both sides of the first sheet material F1 withtransmitted light or reflected light, a method of performing imaging andimage processing with a polarizing film for inspection arranged in acrossed Nicols relationship (also referred to as “0° cross”) with thepolarization axis of the polarizing plate (the object to be inspected)between a CCD camera and the object, or a method of performing imagingand image processing with a polarizing film for inspection arranged at acertain angle (for example, in the range of more than 0° to 10°, alsoreferred to as “x° cross”) with the polarization axis of the polarizingplate (the object to be inspected) between a CCD camera and the object.Known methods may be used for the image processing algorithm. Forexample, defects may be detected by grayscale determination based onbinarization.

The method of performing imaging and image processing with transmittedlight allows the detection of contaminants in the first sheet materialF1. The method of performing imaging and image processing with reflectedlight allows the detection of contaminants deposited on the surface ofthe first sheet material F1. In the method of performing imaging andimage processing with 0° cross, surface contaminants, dirt, and interiorcontaminants can generally be detected as bright spots. In the method ofperforming imaging and image processing with X° cross, knicks cangenerally be detected.

Score lines are formed in the first sheet material F1 by cutting thesurface protecting film F13, the pressure-sensitive adhesive layer F15,the first optical film F11, and the first pressure-sensitive adhesivelayer F14 without cutting the first release film F12. As a result, thefirst release film F12 can be used as a carrying medium for the firstoptical film F11. In an embodiment of the invention, therefore, thefirst release film F12 formed on the first optical film F11 with thefirst pressure-sensitive adhesive layer F14 interposed therebetween ispreferably used as a carrying medium to feed the first and secondoptical films F11 and F21 to the first and second bonding steps,respectively. Any type of cutting means may be used to cut part of thefirst sheet material F1, exclusive of the first release film F12.Preferably, the cutting means is horizontally moved in the widthdirection of the first sheet material F1 when part of the first sheetmaterial F1, exclusive of the first release film F12 is cut. The cuttingmeans is preferably, but not limited to, a laser or an edge tool (suchas a circular knife). According to such a method, the cut end surface ofthe portion obtained by cutting part of the first sheet material F1,exclusive of the first release film F12, is made smoother than thatobtained by a conventional method of cutting the material with an edgetool pressed against the material (with the cutting means verticallymoved), so that the end surface do not have to be further processed.

(2) Feeding Step (S2 in FIG. 1). The first sheet material F1 is fed tothe downstream side from the first roll provided and placed. Forexample, a first feeder 12 to feed the first sheet material F1 includesa pair of nip rollers, a tension roller, a rotary drive, an accumulator,a sensor, a controller, and any other unit.

(3) First Optical Film Bonding Step (S3 in FIG. 1). While the firstrelease film F12 is removed using a first peeling apparatus 17, thefirst optical film F11 separated from the first release film F12 isbonded to an optical display unit W with the first pressure-sensitiveadhesive layer F14 interposed therebetween using a first bondingapparatus 18. In this step, the first optical film F11 is divided into apiece by each score line, and the resulting divided piece of the firstoptical film F11 with a size corresponding to that of the opticaldisplay unit W is bonded to the optical display unit W. In the bondingstep, the first optical film F11 and the optical display unit W may bepress-bonded between a pair of rolls as described below.

(4-1) Cleaning Step (S4-1 in FIG. 1). The surface of the optical displayunit W is cleaned by polishing cleaning, water cleaning or any othercleaning techniques. The cleaned optical display unit W is transportedto an inspection apparatus.

(4-2) Inspecting Step (S4-2 in FIG. 1). After the cleaning, the surfaceof the optical display unit W is inspected using an inspectionapparatus. After the inspection, the optical display unit W istransported to the first bonding apparatus 18.

All of the step of providing the first roll, the feeding step, the stepof bonding the first optical film, the cleaning step, and the inspectionstep are preferably performed in a continuous manufacturing line. In theabove series of manufacturing steps, the first optical film F11 isbonded to one side of the optical display unit W. A description is givenbelow of the manufacturing step in which the second optical film F21 isbonded to the other side.

(5) Step of Providing Second Material Roll (S11 in FIG. 1). A secondroll of a second belt-shaped sheet material F2 is provided. As shown inFIG. 4, the laminated structure of the second sheet material F2 istypically, but not limited to, the same as that of the first sheetmaterial. The second sheet material F2 includes a second optical filmF21, a second release film F22, and a surface protecting film F23. Thesecond optical film F21 includes a second polarizer 21 a, a third filmF21 b provided on one side of the polarizer 21 a with an adhesive layer(not shown) interposed therebetween, and a fourth film F21 c provided onthe other side with an adhesive layer (not shown) interposedtherebetween.

For example, the third and fourth films F21 b and F21 c are each apolarizer protecting film (such as a triacetylcellulose film or a PETfilm). The fourth film F21 c is to be bonded to the surface of theoptical display unit W with a second pressure-sensitive adhesive layerF24 interposed therebetween. The third film F21 b may undergo a surfacetreatment. Examples of the surface treatment include a hard coatingtreatment, an antireflection treatment, and a treatment for any otherpurpose such as anti-sticking, diffusion or antiglare purpose. Thesecond release film F22 is provided on the fourth film F21 c with asecond pressure-sensitive adhesive layer F24 interposed therebetween.The surface protecting film F23 is provided on the third film F21 b witha pressure-sensitive adhesive layer F25 interposed therebetween.

In an embodiment of the invention, the second sheet material F2 hasscore lines that are previously formed so that the second optical filmF21 can be divided by the score lines into pieces each having a lengthcorresponding to the short side of the optical display unit. Each scoreline, which extends in the width direction of the second sheet materialF2, is typically formed by cutting the layers other than the secondrelease film F22 in the second sheet material F2. However, the layersother than the second release film F22 in the second sheet material F2do not always have to be completely cut, and for example, at least onelayer such as the second pressure-sensitive adhesive layer F24 may alsobe not completely cut, or the score line may be in any other form suchas a perforation, as long as the second optical film F21 can be dividedby each score line.

The score lines may be formed in the second sheet material F2 in thesame manner as described for the first sheet material F1 using FIGS. 5and 6. The cutting means for use in forming the score lines in thesecond sheet material F2 may be the same as that described above for usein forming the score lines in the first sheet material F1.

(6) Feeding Step (S12 in FIG. 1). The second sheet material F2 is fed tothe downstream side from the second roll provided and placed. Forexample, a second feeder 22 to feed the second sheet material F2includes a pair of nip rollers, a tension roller, a rotary drive, anaccumulator, a sensor, a controller, and any other unit.

(7) Second Optical Film Bonding Step (S13 in FIG. 1). Subsequently,while the second release film F22 is removed using a second peelingapparatus 27, the second optical film F21 separated from the secondrelease film F22 is bonded to the opposite side of the optical displayunit W (from the side where the first optical film F11 is bonded) withthe second pressure-sensitive adhesive layer F24 interposed therebetweenusing a second bonding apparatus 28. In this step, the second opticalfilm F21 is divided into a piece by each score line, and the resultingdivided piece of the second optical film F21 with a size correspondingto that of the optical display unit W is bonded to the optical displayunit W. Before the second optical film F21 is bonded to the opticaldisplay unit W, the optical display unit W may be turned by 90° usingthe feed direction-switching mechanism of the feeding mechanism so thatthe first and second optical films F11 and F21 can have a crossed Nicolsrelationship.

(8) Transporting and Feeding Step (S5 in FIG. 1). Preferably, themanufacturing method of the invention further includes a transportingand feeding step between the first optical film bonding step and thesecond optical film bonding step, and the transporting and feeding stepincludes the step of turning the optical display unit from the directionof bonding in one of the first and second bonding apparatuses to thedirection of bonding in the other bonding apparatus. In addition to theturning step, the transporting and feeding step may further include thestep of turning over the optical display unit. In an embodiment of theinvention, the transporting and feeding step preferably includes thestep of turning the optical display unit W, which has undergone thefirst bonding step, to the direction of bonding in the second bondingstep. In a preferred embodiment of the invention, the turning step isperformed so that the direction of the long side of the first opticalfilm F11 bonded to the optical display unit W can make an angle of 0±5°,preferably 0±1°, with the direction of the long side of the secondoptical film F21 to be bonded. For example, when the direction of thefirst optical film F11-feeding line is parallel to the direction of thesecond optical film F21-feeding line (including when they are on astraight line), the turning angle in the turning step is preferably from85° to 95°. In the bonding step, the second optical film F21 and theoptical display unit W may be press-bonded between a pair of rolls asdescribed below.

(9) Step of Inspecting Optical Display Device (S14 in FIG. 1). Aninspection apparatus is used to inspect an optical display deviceincluding the optical display unit W and the optical films bonded toboth sides of the optical display unit W. An example of the inspectionmethod is a method of performing imaging and image processing withreflected light on both sides of the optical display device. Anotherexample of the method uses a polarizing film for inspection placedbetween a CCD camera and the object to be inspected. Known methods maybe used for the image processing algorithm. For example, defects may bedetected by grayscale determination based on binarization.

(10) Defect information obtained by the inspection apparatus is used todetermine whether the optical display device is non-defective. Theoptical display device determined to be non-defective is transferred tothe next implementing process. When determined to be defective, it issubjected to a reworking process, in which a new optical film is bonded,and then the product is inspected. The product determined to benon-defective is transferred to the implementing process, but theproduct determined to be defective is subjected to the reworking processagain or to disposal.

In the above series of manufacturing steps, the first optical film F11bonding step and the second optical film F21 bonding step may beperformed in a continuous manufacturing line, which makes it possible tomanufacture the optical display device in a satisfactory manner.

Configuration of the Whole of Manufacturing System

Next, a description is given of the configuration of the whole of themanufacturing system of the invention. The manufacturing system of theinvention is a system for manufacturing an optical display deviceincluding an optical display unit and an optically-anisotropic opticalfilm bonded thereto, preferably a system for manufacturing an opticaldisplay device including an optical display unit and an optical filmthat includes a polarizing plate and is bonded to the optical displayunit. The manufacturing system of the invention includes a first bodingapparatus for performing the first bonding step and a second bondingapparatus for performing the second bonding step.

FIG. 3 shows an exemplary system according to an embodiment of theinvention including an optical display unit W feeding apparatus M1, afirst optical film F11 feeding apparatus M2, a first bonding apparatusM3 for bonding the first optical film F11, a transporting and feedingapparatus M4 for transporting and feeding the optical display unit Wafter the bonding, a second optical film F21 feeding apparatus M5, and asecond bonding apparatus M6 for bonding the second optical film F21.

Concerning this embodiment, FIG. 3 shows an example where the firstoptical film F11 feeding apparatus M2, the first bonding apparatus M3,the transporting and feeding apparatus M4, the second optical film F21feeding apparatus M5, and the second bonding apparatus M6 are linearlyarranged, and the feeding apparatus M1 is placed so that the opticaldisplay unit W can be fed in a direction perpendicular to the directionof the flow of the optical display unit W in the first bonding apparatusM3.

Configuration of Each Section in the Manufacturing System

An example of the configuration of each section in the manufacturingsystem of the invention is described below.

The manufacturing system of the invention includes the optical displayunit W feeding apparatus M1 for feeding the optical display unit W.

The manufacturing system of the invention includes the first opticalfilm feeding apparatus M2 for drawing and feeding the first sheetmaterial F1 from a roll of the first sheet material F1 including thefirst optical film F11. This embodiment shows an example where the firstoptical film feeding apparatus M2 includes a first feeder 12.

The first roll of the first sheet material F1 is mounted on a roll mountapparatus that is geared to a motor or the like to rotate freely or at acertain speed. A controller 1 is provided to set the rotational speedand to control the drive.

The first feeder 12 is a feeding mechanism to feed the first sheetmaterial F1 to the downstream side. The first feeder 12 is controlled bythe controller 1.

The manufacturing system of the invention includes the first bondingapparatus 18 (M3) for bonding the first optical film F11, which is fedfrom the first optical film feeding apparatus M2, to one surface of theoptical display unit W, which is fed from the optical display unit Wfeeding apparatus M1. This embodiment shows an example where the firstbonding apparatus 18 (M3) includes a press roller, a guide roller, afirst peeling apparatus 17, and a first removing apparatus 19. The firstremoving apparatus 19 forms a defective portion removing mechanism toremove a defective divided piece of the optical film, but such aremoving mechanism may be omitted.

The first bonding apparatus 18 bonds part of the first sheet material F1(the first optical film F11), from which the release film F12 has beenpeeled off by the first peeling apparatus 17, to the optical displayunit W with the first pressure-sensitive adhesive layer F14 interposedtherebetween. The first sheet material F1 feeding route is placed abovethe optical display unit W feeding route.

In the bonding process, the first optical film F11 is bonded to thesurface of the optical display unit W, while it is pressed against thesurface by the press roller and the guide roller. The pressure from thepress roller and the guide roller and the driving operation thereof arecontrolled by the controller 1.

The first peeling apparatus 17 has a peeling mechanism that isconfigured so that the first release film F12 can be peeled off byreversing the feeding direction of the first release film F12 and thatpart of the first sheet material F1 (the first optical film F11) peeledoff from the first release film F12 can be fed to the surface of theoptical display unit W. After peeled off, the release film F12 is woundaround a roll. The winding around the roll is controlled by thecontroller 1.

Specifically, in an embodiment of the invention, the first optical filmfeeding apparatus M2 has a feeding mechanism that feeds the firstoptical film F11 to the first bonding apparatus M3 by using, as acarrying medium, the first release film F12, which is provided on thefirst optical film F11 with the pressure-sensitive adhesive layer F14interposed therebetween.

The bonding mechanism includes a press roller and a guide roller opposedthereto, which are provided at the bonding position. The guide rollercomprises a rubber roller whose rotation is driven by a motor, and isprovided movable upward and downward. The press roller, which isprovided movable upward and downward immediately above the guide roller,comprises a metallic roller whose rotation is driven by a motor. Whenthe optical display unit W is fed to the bonding position, the pressroller is elevated to a position higher than the upper surface so thatthe space between the rollers is widened. Alternatively, the guideroller and the press roller may each be a rubber roller or a metallicroller. As described above, the system is configured so that the opticaldisplay unit W can be cleaned by any type of cleaning apparatus and fedby a feeding mechanism. The feeding mechanism is also controlled by thecontroller 1.

A description is given of the first removing apparatus 19 for removing adefective portion of the first sheet material F1. When the first sheetmaterial F1 having a defect is transported to the bonding position, theguide roller moves vertically downward. Subsequently, a roller overwhich a remover film is looped moves to the regular position of theguide roller. The press roller is allowed to move vertically downward topress the defective portion of the first sheet material F1 against theremover film. The defective portion of the first sheet material F1 isattached to the remover film and wound around a roller together with theremover film. The remover film can adhere to the defective portion ofthe first sheet material F1 by using the adhesive power of the firstpressure-sensitive adhesive layer F14 of the first sheet material F1.Alternatively, however, a pressure-sensitive adhesive tape may be usedas the remover film.

The optical display unit W to which the first optical film F11 is bondedas described above is fed to the downstream side, where the secondoptical film F21 (the second sheet material F2) is bonded thereto.Hereinafter, the same apparatus configuration will be described briefly.

The manufacturing system of the invention preferably further includes atransporting and feeding apparatus M4 placed between the first andsecond bonding apparatuses. The transporting and feeding apparatus M4 isan apparatus for transporting and feeding the optical display unit fromone of the first and second bonding apparatuses to the other. The feederpreferably has a turning mechanism 20 that turns the optical displayunit W from the direction of bonding in one of the first and secondbonding apparatuses to the direction of bonding in the other bondingapparatus. Besides the turning mechanism 20, the feeder may furtherinclude a turning-over mechanism for turning over the optical displayunit.

For example, when the second optical film F21 is bonded in a 90°relationship (crossed Nicols relationship) with the first optical filmF11, the optical display unit W is turned by 90° by the feedingdirection-switching mechanism (turning mechanism 20) of the feedingmechanism, and then the second optical film F21 is bonded thereto. Themethod described below for bonding the second sheet material F2 includesperforming each step, while keeping the second sheet material F2 turnedupside down (with the second release film F22 facing upward), andbonding the second optical film F21 to the lower side of the opticaldisplay unit W.

The manufacturing system of the invention includes the second opticalfilm feeding apparatus M5 for drawing and feeding the second sheetmaterial F2 from a roll of the second sheet material F2 including thesecond optical film F21. This embodiment shows an example where thesecond optical film feeding apparatus M5 includes a second feeder 22.

The second roll of the second sheet material F2 is mounted on a rollmount apparatus that is geared to a motor or the like to rotate freelyor at a certain speed. The controller 1 is provided to set therotational speed and to control the drive.

The second feeder 22 is a feeding mechanism to feed the second sheetmaterial F2 to the downstream side. The second feeder 22 is controlledby the controller 1.

The manufacturing system of the invention includes the second bondingapparatus 28 (M6) for bonding the second optical film F21, which is fedfrom the second optical film feeding apparatus M5, to the other surfaceof the optical display unit W, which is fed from the transporting andfeeding apparatus M4. This embodiment shows an example where the secondbonding apparatus 28 (M6) further includes a press roller, a guideroller, a second peeling apparatus 27, and a second removing apparatus29. The second removing apparatus 29 forms a defective portion removingmechanism to remove a defective divided piece of the optical film, butsuch a removing mechanism may be omitted.

The second bonding apparatus 28 bonds part of the second sheet materialF2 (the second optical film F21), from which the second release film F22has been peeled off by the second peeling apparatus 27, to the opticaldisplay unit W with the second pressure-sensitive adhesive layer F24interposed therebetween. In the bonding process, the second optical filmF21 is bonded to the surface of the optical display unit W, while it ispressed against the surface by the press roller and the guide roller.The pressure from the press roller and the guide roller and the drivingoperation thereof are controlled by the controller 1.

The second peeling apparatus 27 has a peeling mechanism that isconfigured so that the second release film F22 can be peeled off byreversing the feeding direction of the second release film F22 and thatpart of the second sheet material F2 (the second optical film) peeledoff from the second release film F22 can be fed to the surface of theoptical display unit W. After peeled off, the release film F22 is woundaround a roll. The winding around the roll is controlled by thecontroller 1.

Specifically, in an embodiment of the invention, the second optical filmfeeding apparatus M5 has a feeding mechanism that feeds the secondoptical film F21 to the second bonding apparatus M6 by using, as acarrying medium, the second release film F22, which is provided on thesecond optical film F21 with the second pressure-sensitive adhesivelayer F24 interposed therebetween.

The bonding mechanism includes a press roller and a guide roller opposedthereto, which are provided at the bonding position. The guide rollercomprises a rubber roller whose rotation is driven by a motor, and isprovided movable upward and downward. The press roller, which isprovided movable upward and downward immediately under the guide roller,comprises a metallic roller whose rotation is driven by a motor. Whenthe optical display unit W is fed to the bonding position, the pressroller is shifted to a lower position so that the space between therollers is widened. Alternatively, the guide roller and the press rollermay each be a rubber roller or a metallic roller.

A description is given of the second removing apparatus 29 for removinga defective portion of the second sheet material F2. When the secondsheet material F2 having a defect is transported to the bondingposition, the guide roller moves vertically upward. Subsequently, aroller over which a remover film is looped moves to the regular positionof the guide roller. The press roller is allowed to move verticallyupward to press the defective portion of the second sheet material F2against the remover film. The defective portion of the second sheetmaterial F2 is attached to the remover film and wound around a rollertogether with the remover film.

The optical display device formed by bonding the first and second sheetmaterials to the optical display unit W is fed to an inspectionapparatus. The inspection apparatus inspects both sides of the opticaldisplay device transported thereto. A light source and a half mirror areused to vertically illuminate the upper surface of the optical displaydevice, and the reflected light is captured as image data by a CCDcamera. Another light source is used to illuminate, at a predeterminedangle, the surface of the optical display device, and the reflectedlight is also captured as image data by the CCD camera. The oppositesurface of the optical display device may also be inspected using alight source and a CCD camera. These image data are subjected to imageanalysis to determine whether the product is non-defective.

For example, the timing of the operation of each apparatus is calculatedby a detecting method using sensors placed at specific locations or by amethod of detecting the rotating part of the feeder or the feedingmechanism with a rotary encoder or the like. The controller 1 may beimplemented in cooperation with software programs and hardware resourcessuch as CPU and memories. In this case, program software, procedures,various settings, etc. are previously stored in memories. Privatecircuits, firmware, or the like may also be used for the implementation.

The optical display device obtained by the manufacturing method of theinvention includes the optical display units and the optical filmsbonded to both sides of the optical display unit. The optical displaydevice can be used as an image display such as a liquid crystal display,an organic electroluminescence (EL) display, or a plasma display panel(PDP).

The liquid crystal display may be formed according to conventionaltechniques. Specifically, the liquid crystal display is usually formedby assembling a liquid crystal cell (corresponding to the opticaldisplay unit) and optical films, and optional components such as alighting system and incorporating a driving circuit, according to anyconventional techniques, except that the optical films are usedaccording to the invention. The liquid crystal cell to be used may alsobe of any type such as TN (Twisted Nematic) type, STN (Super TwistedNematic) type, or n type. In particular, a VA (Vertical Alignment) orIPS (In-Plane-Switching) mode liquid crystal cell is effectively used inan embodiment of the invention.

Any appropriate liquid crystal display may be formed such as a liquidcrystal display including a liquid crystal cell and the optical filmplaced on one or both sides of the liquid crystal cell or a liquidcrystal display using a backlight or a reflector in the lighting system.In that case, the optical film or films may be placed on one or bothsides of the liquid crystal cell. The optical films placed on both sidesmay be the same or different. In the process of forming the liquidcrystal display, one or more layers of an additional appropriatecomponent or components such as a diffusion plate, an antiglare layer,an anti-reflection film, a protective plate, a prism array, a lens arraysheet, a light diffusion plate, and a backlight may also be placed at anappropriate location or locations.

The optical film or films may be placed on one or both sides of a liquidcrystal cell to form a liquid crystal display having an appropriatestructure according to conventional techniques, such as a transmissive,reflective or transflective liquid crystal display. Therefore, theliquid crystal cell used to form a liquid crystal display may be of anytype. Any appropriate type of liquid crystal cell such as an activematrix driving type typified by a thin film transistor type may be used.

The polarizing plates or the optical components provided on both sidesof a liquid crystal cell may be the same or different. In the process offorming a liquid crystal display, one or more layers of an additionalappropriate component or components such as a prism array sheet, a lensarray sheet, a light diffusion plate, and a backlight may be placed atan appropriate location or locations.

Bonding Methods Performed Using Turn According to Other Embodiments

The embodiment described above shows a case where one of the first andsecond optical films F11 and F21 is bonded to the optical display unit Wfrom the upper side, and the other is bonded to the optical display unitW from the lower side. Alternatively, the system may be configured sothat both the first and second optical films F11 and F21 can be bondedto the optical display unit W from one of the upper and lower sides. Inthis case, the process may include bonding the first optical film F11 toone surface of the optical display unit W from the upper or lower side,then turning the optical display unit W so that it can be turned overand rotated, and bonding the first optical film F11 to the othersurface. For example, the turning may be performed in such a manner thatthe optical film is turned over and rotated by 90°, which makes itpossible to bond the first and second optical films F11 and F21 in acrossed Nicols relationship with each other.

FIG. 7 is a schematic diagram showing examples of the method of turningthe optical display unit W in such a manner that it is turned over androtated by 90°. Parts (a) and (b) of FIG. 7 show methods in which theoptical display unit W is turned over so as to have a 90° relationship.Part (a) shows an example where the optical display unit W is turnedover around a horizontal rotation axis A1 passing through a corner ofthe optical display unit W, and part (b) shows an example where theoptical display unit W is turned over around a horizontal rotation axisA2 passing through the center of the optical display unit W. Part (c) ofFIG. 7 shows a method in which turning over and rotation are performedin two stages so that a 90° relationship can be achieved, wherein theturning over and the rotation may be performed in any order. Part (d) ofFIG. 7 shows a method in which rotation is performed to achieve a 90°relationship, while turning over is performed, using a turning mechanism20 including a mechanism for rotating the optical display unit W in ahorizontal plane and a mechanism for turning over the optical displayunit W around a horizontal rotation axis A3.

The terms “rotated by 90°” and “a 90° relationship” mean a state orrelationship where the long side of the optical display unit W after theturning is parallel to the short side before the turning and the shortside of the optical display unit W after the turning is parallel to thelong side before the turning. It will be understood that the method ofturning the optical display unit W is not limited to the modes shown inFIG. 7 and the optical display unit W may be turned over and rotated by90° in any other mode.

In the embodiment described above, after bonded in the first bondingapparatus 18, the optical display unit W is turned to the bondingdirection in the second bonding apparatus 28. Alternatively, as statedabove, the second optical film F21 may be bonded to the optical displayunit W prior to the first optical film F11. In this case, the opticaldisplay unit W after the bonding in the second bonding apparatus 28 maybe turned to the bonding direction in the first bonding apparatus 18.

Manufacturing Systems According to Other Embodiments

In the manufacturing system of the invention, the respective apparatusesmay be arranged in any order. For example, the optical display unit Wfeeding apparatus M1, the first optical film F11 feeding apparatus M2,and the first bonding apparatus M3 may be linearly arranged, and thesecond optical film F21 feeding apparatus M5 and the second bondingapparatus M6 may be arranged parallel to the linearly arrangedapparatuses. The transporting and feeding apparatus M4 may be placedbetween the first and second bonding apparatuses M3 and M6.

In an embodiment of the invention, when no mechanism is provided forturning the optical display unit W, the first optical film F11 feedingapparatus M2 and the first bonding apparatus M3 are preferably arrangedperpendicular to the second optical film F21 feeding apparatus M5 andthe second bonding apparatus M6.

DESCRIPTION OF REFERENCE CHARACTERS

In the drawings, reference character F1 represents a first sheetmaterial, F2 a second sheet material, F11 a first optical film, F11 a afirst polarizer, F11 b a first film, F11 c a second film, F12 a firstrelease film, F13 a surface protecting film, F14 a firstpressure-sensitive adhesive layer, F21 a second optical film, F21 a asecond polarizer, F21 b a third film, F21 c a fourth film, F22 a secondrelease film, F23 a surface protecting film, F24 a secondpressure-sensitive adhesive layer, M1 an optical display unit feedingapparatus, M2 a first optical film feeding apparatus, M3 a first bondingapparatus, M4 a transporting and feeding apparatus, M5 a second opticalfilm feeding apparatus, M6 a second bonding apparatus, 1 a controller,12 a first feeder, 17 a first peeling apparatus, 18 a first bondingapparatus, 19 a first removing apparatus, 20 a turning mechanism, 22 asecond feeder, 27 a second peeling apparatus, 28 a second bondingapparatus, 29 a second removing apparatus, and W an optical displayunit.

1. A system for manufacturing an optical display device comprising a rectangular optical display unit and an optically-anisotropic optical film bonded to the optical display unit, comprising: a first bonding apparatus for bonding a divided piece of a first optical film to one surface of an optical display unit, wherein the divided piece of the first optical film has a length corresponding to a long side of the optical display unit and is obtained from a roll of a belt-shaped sheet material that comprises the first optical film and has score lines that are previously formed so that the first optical film can be divided by the score lines into pieces each having a length corresponding to the long side of the optical display unit, wherein the first optical film has a width corresponding to a short side of the optical display unit; and a second bonding apparatus for bonding a divided piece of a second optical film to another surface of the optical display unit, wherein the divided piece of the second optical film has a length corresponding to the short side of the optical display unit and is obtained from a roll of a belt-shaped sheet material that comprises the second optical film and has score lines that are previously formed so that the second optical film can be divided by the score lines into pieces each having a length corresponding to the short side of the optical display unit, wherein the second optical film has a width corresponding to the long side of the optical display unit.
 2. A system for manufacturing an optical display device comprising a rectangular optical display unit and an optical film including a polarizing plate and bonded to the optical display unit, comprising: an optical display unit feeding apparatus for feeding the optical display unit; a first optical film feeding apparatus for drawing and feeding a belt-shaped sheet material from a roll of the belt-shaped sheet material, wherein the belt-shaped sheet material comprises a first optical film with a width corresponding to a short side of the optical display unit and has score lines that are previously formed so that the first optical film can be divided by the score lines into pieces each having a length corresponding to a long side of the optical display unit; a first bonding apparatus for bonding a divided piece of the first optical film to one surface of the optical display unit, wherein the optical display unit is fed from the optical display unit feeding apparatus, and the first optical film is fed from the first optical film feeding apparatus; a feeder for transporting and feeding the optical display unit after the bonding of the first optical film; a second optical film feeding apparatus for drawing and feeding a belt-shaped sheet material from a roll of the belt-shaped sheet material, wherein the belt-shaped sheet material comprises a second optical film with a width corresponding to the long side of the optical display unit and has score lines that are previously formed so that the second optical film can be divided by the score lines into pieces each having a length corresponding to the short side of the optical display unit; and a second bonding apparatus for bonding a divided piece of the second optical film to another surface of the optical display unit, wherein the optical display unit is fed from the feeder, and the second optical film is fed from the second optical film feeding apparatus.
 3. The system according to claim 2, wherein the feeder has a turning mechanism for turning the optical display unit to a bonding direction for the second bonding apparatus after the bonding in the first bonding apparatus.
 4. The system according to claim 2 or 3, wherein the first and second optical film feeding apparatuses each has a defective portion removing mechanism for removing a defective divided piece of the optical film.
 5. The system according to claim 2 or 3, wherein the first and second optical film feeding apparatuses have feeding mechanisms for feeding the first and second optical films to the first and second bonding apparatuses, respectively, by using, as a carrying medium, a release film which is provided on the optical film with a pressure-sensitive adhesive layer interposed therebetween.
 6. A method for manufacturing an optical display device comprising a rectangular optical display unit and an optically-anisotropic optical film bonded to the optical display unit, comprising: a first bonding step comprising: providing a roll of a belt-shaped sheet material that comprises a first optical film with a width corresponding to a short side of the optical display unit and has score lines that are previously formed so that the first optical film can be divided by the score lines into pieces each having a length corresponding to a long side of the optical display unit; and bonding a divided piece of the first optical film having a length corresponding to the long side of the optical display unit to one surface of the optical display unit; and a second bonding step comprising: providing a roll of a belt-shaped sheet material that comprises a second optical film with a width corresponding to the long side of the optical display unit and has score lines that are previously formed so that the second optical film can be divided by the score lines into pieces each having a length corresponding to the short side of the optical display unit; and bonding a divided piece of the second optical film having a length corresponding to the short side of the optical display unit to another surface of the optical display unit.
 7. The method according to claim 6, further comprising a turning step comprising turning the optical display unit to a bonding direction for the second bonding step after the first bonding step.
 8. The method according to claim 6 or 7, further comprising a defective portion removing step comprising removing a defective divided piece of the optical film when the first and second optical films are each fed.
 9. The method according to claim 6 or 7, wherein the first and second optical films are transported and fed to the first and second bonding steps, respectively, using, as a carrying medium, a release film which is provided on the optical film with a pressure-sensitive adhesive layer interposed therebetween.
 10. A set of material rolls, comprising: a first roll comprising a first optical film to be bonded to one surface of a rectangular optical display unit, the first roll comprising a first belt-shaped sheet material that comprises the first optical film, a first pressure-sensitive adhesive layer, and a first release film laminated in this order, wherein the first optical film comprises a first polarizing plate whose longitudinal direction is parallel to its absorption axis, the first belt-shaped sheet material having score lines that are previously formed so that the first optical film can be divided by the score lines into pieces each having a length corresponding to a long side of the optical display unit, the first belt-shaped sheet material having undergone a slitting process in a direction parallel to the longitudinal direction of the first polarizing plate so that it has a width corresponding to a short side of the optical display unit, and having been wound into the roll; and a second roll comprising a second optical film to be bonded to another surface of the optical display unit, the second roll comprising a second belt-shaped sheet material that comprises the second optical film, a second pressure-sensitive adhesive layer, and a second release film laminated in this order, wherein the second optical film comprises a second polarizing plate whose longitudinal direction is parallel to its absorption axis, the second belt-shaped sheet material having score lines that are previously formed so that the second optical film can be divided by the score lines into pieces each having a length corresponding to a short side of the optical display unit, the second belt-shaped sheet material having undergone a slitting process in a direction parallel to the longitudinal direction of the second polarizing plate so that it has a width corresponding to the long side of the optical display unit, and having been wound into the roll.
 11. The set of material rolls according to claim 10, wherein the optical display unit to be subjected to the bonding is a VA or IPS mode liquid crystal panel.
 12. A method for manufacturing a material roll for use in the set of material rolls according to claim 10 or 11, comprising the steps of: slitting a material having undergone no slitting process to form a belt-shaped sheet material with a width corresponding to the long or short side of the optical display unit, wherein the material comprises an optical film, a pressure-sensitive adhesive layer, and a release film laminated in this order, the optical film comprises a polarizing plate whose longitudinal direction is parallel to its absorption axis, and the slitting is performed parallel to the longitudinal direction of the polarizing plate; and winding the resulting belt-shaped sheet material into a roll.
 13. A material roll comprising an optical film to be bonded to a surface of a rectangular optical display unit, comprising: a belt-shaped sheet material that comprises the optical film, a pressure-sensitive adhesive layer, and a release film laminated in this order, wherein the optical film comprises a polarizing plate whose longitudinal direction is parallel to its absorption axis, the belt-shaped sheet material having score lines that are previously formed so that the optical film can be divided by the score lines into pieces each having a length corresponding to a long or short side of the optical display unit, the belt-shaped sheet material having undergone a slitting process in a direction parallel to the longitudinal direction of the polarizing plate so that it has a width corresponding to the short or long side of the optical display unit, and having been wound into the roll.
 14. A method for manufacturing a material roll comprising an optical film to be bonded to a surface of a rectangular optical display unit, comprising the steps of: slitting a material having undergone no slitting process to form a belt-shaped sheet material with a width corresponding to a short or long side of the optical display unit, wherein the material comprises the optical film, a pressure-sensitive adhesive layer, and a release film laminated in this order and has score lines that are previously formed so that the optical film can be divided by the score lines into pieces each having a length corresponding to the long or short side of the optical display unit, the optical film comprises a polarizing plate whose longitudinal direction is parallel to its absorption axis, and the slitting is performed parallel to the longitudinal direction of the polarizing plate; and winding the resulting belt-shaped sheet material into a roll.
 15. A method for manufacturing an optical display device comprising an optical film including a polarizing plate and a rectangular optical display unit having a surface to which the optical film is bonded, comprising the steps of: providing a material roll that is a roll of a belt-shaped sheet material obtained by slitting a material having undergone no slitting process into a width corresponding to a short or long side of the optical display unit, wherein the material comprises the optical film, a pressure-sensitive adhesive layer, and a release film laminated in this order and has score lines that are previously formed so that the optical film can be divided by the score lines into pieces each having a length corresponding to the long or short side of the optical display unit, the optical film comprises a polarizing plate whose longitudinal direction is parallel to its absorption axis, and the slitting is performed parallel to the longitudinal direction of the material; drawing the belt-shaped sheet material from the material roll; and bonding a divided piece of the optical film to a surface of the rectangular optical display unit.
 16. A system for manufacturing an optical display device comprising an optical film including a polarizing plate and a rectangular optical display unit having a surface to which the optical film is bonded, comprising: a bonding apparatus for drawing a belt-shaped sheet material from a roll of the belt-shaped sheet material and bonding a divided piece of the optical film to the rectangular optical display unit, wherein the belt-shaped sheet material is obtained by slitting a material having undergone no slitting process into a width corresponding to a short or long side of the optical display unit, wherein the material comprises the optical film, a pressure-sensitive adhesive layer, and a release film laminated in this order and has score lines that are previously formed so that the optical film can be divided by the score lines into pieces each having a length corresponding to the long or short side of the optical display unit, the optical film comprises a polarizing plate whose longitudinal direction is parallel to its absorption axis, and the slitting is performed parallel to the longitudinal direction of the material. 